It has been known that articles can be conveniently marked by firing from a gun or like instrument a rupturable projectile containing a marking liquid. Such projectiles are designed to rupture or break on impact with the article to be marked. Such marking projectiles have generally comprised a soft gelatin capsule containing a marking liquid in the form of a liquid paint or paint-like composition. Such marking projectiles are disclosed, for example, in U.S. Pat. No. 3,861,943 issued Jan. 21, 1975 to Norman Grainger and assigned to R. P. Scherer Limited.
While the use of such projectiles for marking articles was a significant advance from the previous methods of dusting articles with powder or providing cuts in the articles in order to identify them, the use of such projectiles has not been entirely satisfactory for a number of reasons. For example, the commercially available marking formulations heretofore employed in the projectiles have generally been oil based paints, such as the pink-pigmented fluorescent oil-based paint mentioned in the aforementioned U.S. Pat. No. 3,861,943. When it is desired to produce only temporary or washable marks on articles such marking compositions are not biodegradable and thus could present undesirable environmental problems.
Also, projectiles containing such marking compositions have had undesirable shelf-life properties and tend to deteriorate on storage. Another significant drawback recognized with such projectiles is that the spherical gelatin capsules containing such marking liquids are not truly spherical but instead tend to become distorted in shape. Such projectiles are normally fired from a compressed gas gun, such as an air gun, and the distorted capsules are not accurately propelled due at least in part both to the escape of compressed gas around the distorted spherical capsule in the barrel of the gun and the curves and erratic turns caused by the distorted spherical capsule in flight.
Additionally, the poor suspension characteristics of the colorants in the marking liquids also has led to nonaccurate shooting of projectiles containing such marking liquids.
Moreover, the composition of such marking liquids has adversely affected the brittleness and friability characteristics of the projectiles leading to breaking of the projectiles during handling or firing of the gun or the projectile becoming not fragile enough to break when impacting the target article.
Other significant drawbacks to such prior marking liquids have been their toxicity and the undesirable presence of hydrocarbon, lower molecular weight alcohols, ketone, ester and chlorinated hydrocarbon solvents and heavy metal compounds which not only can cause softening and deterioration of soft gelatin capsules but also are not suitable for release into the environment.
It is therefore an object of this invention to provide marking compositions for incorporation into projectiles such as soft gelatin capsules, which marking compositions substantially eliminate the drawbacks and problems of the aforementioned marking compositions. A further objective of this invention is to provide projectiles that avoid the drawbacks and problems of the aforementioned projectiles.